NRC1 a central regulator of defence against pathogens

We have recently identified a tomato NB-LRR protein that unlike many other characterised NB-LRRs does not seem to function as an immune receptor, but as a central regulator in the defence signal transduction cascade downstream of immune receptors. A striking observation is that NRC1 not only acts downstream of multiple intracellularly localized NB-LRRs, but also downstream of extracellularly localized receptor-like proteins (RLPs). NRC1 was identified as an up-regulated gene in Cf-4/Avr4 seedlings mounting a hypersensitive response (HR), a defence-associated type of cell death. You can see a movie of these plants on our introductory page. These seedlings were produced by crossing two different parents: one containing the immune receptor Cf-4 and the other the avirulence protein Avr4 from Cladosporium fulvum. The constitutive production of both proteins in these seedlings triggers a systemic HR.
NRC1 from tomato is an NB-LRR protein that acts downstream of multiple intracellularly localized NB-LRRs and extracellular receptor-like proteins (RLPs). Virus-induced gene silencing (VIGS) of NRC1 in Nicotiana benthamiana compromises the HR induced by different R/Avr gene pairs and by a constitutively active form of Mi-1 (Mi-1T557S). Red circles: HR; yellow circles: compromised HR. Silencing of the co-chaperone SGT1 was used as a positive control.
Virus-induced gene silencing (VIGS) using recombinant tobacco rattle virus (TRV) containing a fragment of NRC1 in Nicotiana benthamiana compromised the HR induced by different R/Avr protein pairs, and the gene therefrom derived its name: NB-LRR Required for HR-associated Cell death 1 (NRC1). When NRC1 is silenced by VIGS in tomato, not only the HR is compromised, but also Cf-4-mediated resistance to C. fulvum carrying Avr4 is attenuated. This project focuses on whether we can use NRC1 to generate broad-spectrum resistance to pathogens, for example by enhancing its defence signalling activity. Furthermore we want to know at the molecular and biochemical level how NRC1 exactly functions in the cell. Similar to our project on Rx, we want to identify NRC1-interacting proteins to determine how NRC1 transduces the defence signals downstream of immune receptors and where NRC1 is positioned in this signal transduction pathway leading to plant resistance.